裂变率测量中的杂质影响及其消除方法

核裂变法是通过测量中子进行裂变率测量的重要方法．常用于热中子测量的裂变室有２３５Ｕ裂变室和２３９Ｐｕ裂变室，快中子测量可以用２３８Ｕ、２３２Ｔｈ和２３７Ｎｐ等裂变室．通常用于裂变室的可裂变核素是采用同位素分离方法或人工方法得到的，其中含有少量其他核素杂质．实验测量表明，少量能发生热裂变的杂质对快中子的测量有很大影响。利用热裂变修正方法和裂变室包镉方法可以消除这种影响。

Effect of the Impurity on the Results of the Fission Rate Measurements and Elimination Method

The nuclear fission method is an imPOrtant method of the fission rate by neutron measurement. The 235U and 239Pu fission chamber can be used to measure the thermal neutron, and 238U, 232Th and 237Np fission chamber are often used to measure the fast neutron. Because the materials making the fission chambers are got by the isotope separation or artificial method,they can contain a few other impurity atoms. The experimetal measurements show that the measurement results for the fast neutron can be obviously affected by the few impurities which can be fissioned by the thermal neutron. The thermal fission can be corrected by the method of the thermal fission correction. It also can be eliminated by using the fast fission chamber with Cd.